By dividing the total number of minutes from the distance flown, we get the speed at which an aircraft is flying. But there is more to its speed than such simple maths.

For example, an A320 aircraft that can carry up to 180 passengers cruises at a speed of 400-500 nautical miles per hour or knots (645-805 kmph). However, high speed can only be achieved at a higher altitude. For an aircraft to achieve the 645 kmph range, it will need to fly at an altitude of about 36,000ft. That’s not all. The speed of an aircraft is also dependent on the wind and the elements as well.

Speed measurements:

Ground speed: It is the time one takes to cover a certain distance over the ground. For example, at cruise altitude, aeroplanes might have a ground speed of 300–600 knots (555-1,110 kmph). However, the wind can alter the speed at which the aircraft passes over the ground. A tailwind pushes the aircraft along at a faster speed while a headwind slows down the aircraft speed across the ground.

Airspeed: An aircraft sitting on the runway usually has a 32 kmph headwind as the airspeed is a measure of the speed of the air over the wing. The speed of the air travelling over the wing dictates how much lift the wing is producing, and it is this lift that allows the aircraft to support its own weight and allows it to fly, according to flightdeckfriend.com .

Pilots always make a reference to their airspeed rather than ground speed as it is the airspeed that keeps the aircraft flying. The ground speed is a by-product. In principle, if you had about a 225 km per hour headwind the aircraft could lift off the ground without moving forward.

(Sources: Aero Corner, FlightDeckFriend.com)

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